AQA Combined - Chemistry Paper 1

• There are about a hundred different elements and they are shown in the periodic table
• Compounds


  Formed when elements combine together in chemical reactions, contain two or more elements chemically combined in fixed proportions
• Fixed proportions


  The same ratio of elements, shown by the formula
• Naming compounds from formula

  1. Take name of metal as is

  2. Take first syllable of non-metal

  3. Add 'ide' for ionic compounds

  4. Add 'ate' if oxygen is present
• Mixture


  Two or more elements or compounds that are not chemically combined together
• Physical separation processes


  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Filtration


  • Separates insoluble solids from liquids, solid residue left on filter paper, liquid filtrate passes through
• Crystallisation

  • Separates soluble solids from liquids, liquid evaporates leaving solid crystals behind
• Simple distillation


  • Separates liquids based on boiling point
• Fractional distillation


  • Separates a mixture of liquids based on different boiling points, uses a fractionating column
• Chromatography


  • Separates liquids based on solubility, uses a stationary phase and a mobile phase
• Atom


  Smallest part of an element that can exist and still be that element, contains protons, neutrons and electrons
• Average size of an atom is about 0.1 nanometres, but the nucleus is only one ten-thousandth of the diameter of the atom
• Electrons have a very small but not zero mass
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Calculating relative atomic mass of a sample with isotopes


  ((isotope abundance x atomic mass number) + (isotope abundance x atomic mass number)) ÷ sum of abundance of all the isotopes
• Dalton model


  Atoms are indivisible, hard spheres
• Thomson model (plum pudding)


  Atoms have a positive charge with electrons embedded in it
• Rutherford model


  Atoms have a tiny, dense, positive nucleus surrounded by empty space with electrons orbiting
• Bohr model


  Electrons orbit the nucleus in distinct shells at different energy levels
• Periodic table


  Elements arranged in order of atomic number (protons), elements with similar properties in vertical groups
• Originally periodic table was arranged by atomic weight, not atomic number, leading to some issues
• Groups in periodic table

  • Group 1 (alkali metals)
  • Group 2 (alkaline earth metals)
  • Group 7 (halogens)
  • Group 0 (noble gases)
• Group


  Vertical column in periodic table, elements have same number of electrons in outer shell and similar properties
• Electrons in outer shell


  Determines how an element reacts with other elements
• The periodic table hasn't always been laid out like this
• Initially, elements were arranged according to their atomic weight, which led to some problems
• Dmitri Mendeleev left gaps in the periodic table and made predictions about undiscovered elements, which turned out to be correct
• Metals


  Elements that will react to form positive ions
• Nonmetals

  Elements that will react but won't form positive ions
• Metals


  • Malleable
  • Conductive
  • Have high melting points
• Group 1 (Alkali metals)


  Highly reactive metals that react with water to produce hydrogen gas and a metal hydroxide
• Group 7 (Halogens)


  Elements that exist as diatomic molecules and become more reactive as you go up the group
• Group 0 (Noble gases)


  Elements with full outer shells, making them very stable, and their boiling points increase as you go down the group
• Metallic bonding involves regular rows of positive ions surrounded by a sea of delocalized electrons
• Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming a giant ionic lattice
• Covalent bonding involves the sharing of electron pairs between nonmetal atoms, forming either small covalent molecules or giant covalent structures
• Polymers


  Very long chains of repeating monomer units held together by strong covalent bonds
• Giant covalent structures are made up of thousands of atoms held together by strong covalent bonds
• Monomers


  Repeating units that are held together by strong covalent bonds to form a long chain